Sewage treatment



July 12, 1955 H. N. JENKS sEwAGE TREATMENT 4 Sheets-Shee l Filed April 20, 1951 lNVENTO R HARRY N. JENKS,

BY WMMM 93o] QETREG ATTORNEY July 12, 1955 H. N. JENKS SEWAGE TREATMENT 4 Sheets-Shee 2 Filed April 20, 1951 ATTORNEY 4 Sheets-Shes". I5

SECONDARY MIXING-HOLDING TANK I6 lNvx-:N-roR:

HARRY N. JENKS, BY

ATTORNEY mrwgmwd H. N. JENKS SEWAGE TREATMENT July 12, 1955 Filed April 20 1951 DETAINING 0nd MIXING STATION 2O I l g PRIMARY MIXING-HOLDING TANK I5 July 12, 1955 Filed April 20, 1951 DAYS of STAEILITY H. N. JENKS 2,713,028

SEWAGE. TREATMENT 4 Sheets-Sheet 4 DIAGRAM SHOWING RELATIONSHIP OF BIOCHEMICAI. OXYGEN DEMAND REDUCTION AND RECIRCULATION RATE THROUGH SUPERATE COLLOIDER (Acvaed Filter) Critical Phase O I I I I I A 0 ZOO 400 GOO 800 IOOO RATE OF RECIRGULATION Million Gallons per Acre per Day F l G. 5.

INVENTOR:

HARRY N. JENKS, BY

ATTORNEY 'United 7 Ciaims. (Cl. 210-7) This invention relates to the purification and clariiication of sewage, trade and other polluted waste liquids, and more particularly relates to such treatment by the use of what is known generally as the activated sludge system.

In such a system, the sewage or other waste liquid is usually iirst subjected to primary settling to remove the settleable solids, whereupon the effluent from the settler is passed to tanks, called aerators, where the liquid is subjected to diffused air which encourages the formation of the activated sludge. Liquid from the aerators goes into a secondary or final settler Where activated sludge resulting from such aeration is removed from the liquid and returned to the aerators. The eii'luent liquid from the secondary clarier has thus been claried and purified. Sludge from both the primary and secondary settlers is then usually digested or otherwise disposed of.

The invention hereof comprises an improvement on or constitutes an improvement over such a system, which is rather expensive because of the complex structures; because of the expense of the requisite equipment and because of operating expense. So it is an object of this invention to devise a substitute system that signicantly overcomes those disadvantages, and yet retains at least most of the advantages of such a system.

Sewage treatment usually follows one or the other of two general types. One of these is the activated sludge process while the other is the trickling filter process. These are distinguished by Lhe marked dierence in the yielded sludges themselves but operationally by the fact that in the trickling filter process the biologic organisms that are used to treat the sewage are stationary on the discrete stones or cinders that make up the filter bed medium. The bacteria and other biologic organisms of the filter bed form zoogleal films on those stones, and these iilms are of substantial extent. Sewage to be so treated is recycled from a settler and admixed with newly incoming sewage so that while the biologic organisms remain xed, the sewage is brought to them.

n the contrary, in a plant operated in accordance with the activated sludge process, the biologic organisms are maintained in motion through the sewage. Such organisms are established and maintained in an aerating tank whose liquid is well aerated to produce an aerobic environment conducive to activity of such organisms. Sludge from the two processes are noticeably different, activated sludge being more bulky than filter bed sludge, but the former being somewhat more easily digested than the latter. Another difference is observable in the plant efiiuent. In the trickling lter process, or trickling lter bed process as the same is sometimes referred to, efliuent which has been stablized as to its biological oxygen demand (B. C. D.) is not as sparkling clear as is the eiiluent from an activated sludge plant. Yet as a filter bed plant is significantly cheaper both as to installed and operating costs as compared with an activated sludge plant, all of these factors must be correlated in determining which plant should be installed in a particular locality. S0

rates Patent C ice it is another object of this invention to get the benefits of both of these types of plants in what is believed to be an entirely new type of plant or system.

Going back for a moment to these two known types of plants, in the trickling lter bed plant the biologic organisms, which hereinafter for short will be referred to merely as bacteria, are both incubated and run their life cycle within the filter bed where they are in effect xed to the stones of the bed or to their zoogleal jelly thereon. As they are thus immobilized, it is necessary to bring food to them in the form of sewage to be treated, and to remove from them their excrescences. Contrariwise, in an activated sludge plant, the bacteria are both incubated and run their life cycle while being mobilized or moved about and circulated through the sewage on which they feed and convert innocuously into their excrescenes. I have observed that it is easier to incubate the bacteria while fixed to the bed but that it is more effective to circulate them through sewage for the best sewage-treatment results. So it is another object of this invention to accomplish that as a desired end-namely, to incubate the bacteria while fixed on stones of a bed and immediately after incubation remove them by transfer to a detaining-mixing station through which the sewage is circulating.

But in a usual trickling lter bed, which is normally six feet deep or so, the bacteria reproduce and grow in zoogleal iilms on the stones of the bed. These films and the stones themselves reduce the` interstices, so that the rate of dosing of sewage on such a lter bed isV relatively limited. So it is a further object of this invention to prevent the accumulation of any substantial quantity of such iilrns by flushing them off as fast as formed, and to be able to reduce the depth of the bed to be of the order of only one foot in depth made up of larger-than-ordinary stones to maximize the size and extent of the interstices between the stones. Indeed, my use of such a discrete bed is not as the usual trickling lter bed but perhaps in a shallow quick transit or fast through-flow bed which should better be called a colloider and which I have discovered by try-out and use can be employed 'to function as a biologic incubator and an effective aerator while avoiding growth of zoogleal gels on the stones or other bodies of discrete material making up the thin or shallow bed.

In a usual activated sludge plant, the aerator is a tank or place in which diffused air is continually bubbled up through the sewage circulating in the tank. This is expensive, so it is another object to render the use of diffused air unnecessary, by devising holding or detention tanks so arranged that the sewage in them is rapidly recirculated to the abnormally shallow iilter bed or colloider of this invention whereby the sewage is amply aerated in such a manner.

So one feature of this invention relates to the rates of application of sewage or other polluted liquid onto the filter-bed to be higher than anything heretofore considered feasible, as will hereafter appear, while at the same time using for such filter a discrete bed of less depth than heretofore attempted. Another feature comprises using detaining or holding-mixing tanks (with no sedimentation therein) concomitantly with the smaller and shallower discrete bed, which is commercially ad# vantageous becaues a unit of volume of such tanks is far less expensive to build than a unit of volume of aeration tanks as employed in the conventional activated sludge process and the bed can be made more eective thereby. It is a feature of this invention that such tanks have no equipment in them such as sludge rakes, so they are inexpensive to build and to operate. A further feature of this invention resides in the design, operation and control of the units ofV the combination of machines or apparatus used whereby it is possible to realize a maximum number of contacts with the minimized zooglealV films on the discrete rocks or cinders of the bed by each drop of polluted liquid during each unit of time. A further important feature of this invention is the putting into practice of the discoverey that a colloiding operation and an effective entrained aeration, as by flowing organically polluted liquid through a single layer of stones or other such discrete material, is sufficient provided the bed discharge is directly, or in short order, passed to a detaining station fulfilling the dual function of providing the required time of not less than three hours for so-called complete treatment by biologic oxidation (but aplesser time for intermediate treatment), and 4foi keeping the activated sludge in intimate admixture withv and in suspension in the liquid. Y

' A further feature of this invention is that the place or station for holding and mixing from which the liquid and 'sludge are passed to the colloider bed and returned, comprises two sequential continuously vortically rotating or swirling bodies of suchmixture of equal size, into the peripheral portionof which any incoming liquid is submergedly delivered. As to said swirling bodies, one may rotate at speed greater than another. I. have ascertained that the passing of the mixture to the colloider bed and return is such that the mixture makes at least l0 passes to the colloider in the detention time of the mixing station, or stated in another way the rate of recirculation during the period of detention equals at least l0 times the Volume of the detaining and mixing station.

These features are embodied in a plant receiving pollutedliquid and having in closed circuit or cyclic ar rangement a detaining and mixing station and an aeratorcolloider.

Furthermore, in addition to the novel structural features and operative steps just referred to, it is also pointed out herein how the detaining and mixing station is brought into cyclic operative arrangement with a secondary or subsequent settlerthat receives secondary oxidized liquid passed thereto from a low interior section of the secondary holding-mixing tank of the detaining and mixing station, thence through a gravity ow line leading into a secondary or subsequent settlerhaving a high overow Weir for progressively releasing stabilized purifiedl efuent-and which subsequent settler has a return sludge line leading from a low interior portion thereof and equipped with pumping means for delivering the sludge puried thereby into the upper interior portion of a primary holding-mixing tank, with result that the detaining and mixing station and the subsequent settler are brought into cyclic operative arrangement with each other.

Unlike activated sludge plants heretofore, this inventionteaches the divorcing of aeration or sludge-activation-to wit: as heretofore accomplished by the direct injection of air into holding tanks-and instead relies upon a rearranging of the action steps so that the aeration or activation is elected in a high-rate or rapidtransit trickling filter bed, while the agitated holding or detaining function and the mixing function are combined in primary and secondary holding-mixing (and non-aerating) tanks of the detaining and mixing station, -into which the resulting aerated or activated effluent from the rapid-transit bed of discretematerial is gravitatingly delivered. By divorcing the zone of forced aeration from within holding tanks there is avoided a submerged delivery of pumped air against the hydrostatic head of the overlying liquid within that which has nowl become the primary and secondary holding-mixing tanks. The required aeration is made possible by the phenomenally rapid-transit ow through or high recirculation rates from the iiler bed.

In this new concept'where the primary and secondary holding-mixing tanks constituting a detaining and mixing station are employed, there is no sedimentation therein, and they are'in operative combination and cyclic ar- (iii rangement with the super-rate aerating colloider provided by the shallow rapid-transit bed of discrete mato rial; there is only mixing within the tanks, and littleif anyrecirculation between tanks. This follows since all the liquid uprising in the riser, or as otherwise expressed passed from the pump, goes directly to and for distributed delivery across the aerator-colloider bed of discrete material, the function of which is for receiving the recirculating liquid and for aerating the liquid while in transit therethrough and for colloiding the collidable fractions of the transiting liquid.

As a matter of fact the dosing rate for this aerating colloider may be as high as 800 million gallons a day (M. G. A. D.) while the low limit is not substantially less than 200 M. G. A. D. VThis is a dosage rate of all proportion to the dosage rates employed in operations using the heretofore employed trickling filter beds.

Such a plant as that illustrated herein and described hereby is based upon the fact that the detaining and mixing station is the real workshop of the purifyingand clarifying bacteria or other biologic orgauismawhile the only real function of the colloider bed is that of an incubator and of a supplier of dissolved oxygen for the bacteria. It is this concept that makes possible cutting down the volumetric capacity of the bed figuratively to vest-pocket size. The enormous and unprecedented super-rates of application of Yfeed to the tiny colloider bed play their part too in the incubation of myriads of active bacteria and the immediate flushing of them and their jelly into their workshop in the detaining and mixing tank while there is still left to them a significant proportion of their life cycle of the order of twenty minutes or even less. It is for this reason that the super-rates of application Vof liquid to the colloider bed are important. `The rate of dosage is far above anything accepted heretofore and the upper limit is substantially 800 M. G. A. D.. The lower limit is not less than 300 M. G. A. D. and in fact the higher the dosage is above that the better are the results. This dosage should appear to the present-day plant operator as out of all proportion to the small size and very shallow depth of the colloider bed, The yard-stick stated in words is enough liquid fed to realize maximum contacts by a drop of liquid with zoogleal films in one unit of time and as rapid a passage of liquid through the bed as can possibly be obtained. Such rapid passage l consider to be at the rate of 1.4 feet per minute or faster. Another way of saying this is that a drop of sewage liquid should take, in the practice of this invenreturned to the system after being vsettled in the secondary clarifier or settler.

The multitudinous number of very active bacteria are avidly hunvry for food since they must eat continuously and not like vertebrates only intermittently. v Being so avid for food, when they are recycled to the detaining and mixing tank they supplement the bacteria received therein from the colloider bed, with the result that the particles ot turbidity stonesthat make up the bed and the water would backV In other words, the water would That up, causing ponding. cease to trickle or percolate through the stones.

is true, but I found that when more than enough liquid" Jid through and along a recirculated liquid pipe 21 leading to the aerator-colloider 24, having means 27 for receiving the recirculated liquid and for distributively delivering the same over and across the shallow bed of discrete material 25 constituting an important functioning feature of the aerator-colloider 254.. The recirculated liquid distributively delivered to and upon the bed 25 liows through the bed and is delivered as bed discharge which is ultimately received within the sump 28 of a tank 26 that is provided for receiving and holding the bed. From this sump 28 just referred to the bed discharge passes along pipe 2 9 having valve-controlled branching pipe rsections 31 and 33 which respectively submergedly deliver in horizontal tangential directions that quantity of bed discharge passing therethrough and therefrom; a quantity of the bed discharge passes into the upper interior portion of the primary holding-mixing tankr15 and a quantity into the upper interior portion of the secondary holding-mixing tank 16. The branching pipe 31 has a control valve 3i) therein and branch pipe 33 has a control valve 32 therein.

From that which has preceded with relation to the description of the pump which includes the riser conduit section 19, or pump casing section 19 as it may be and is properly referred to, it will be noted that the recirculated liquid line 21 extends from and is in ow pressure communication with the otherwise closed upper end portion of the riser or from that which may be referred to as a discharge casing section of the pump. From this discharge casing section of the pump the recirculated liquid line 21 leads to and discharges into tanks 1S and 16, it will be observed that of these the tangentially disposed liquid feed line 14 and the tangentially disposed branch 31 of the gravity flowrbed discharge line 29 provide gravity delivery into the primary holding' mixing tank 15. The valve-controlled branch delivery section or line 33 andthe pipe section 45 thereof, which merges into the terminal portion of gravity flow feed line 14, provides for the tangential delivery of pumped return sludge from the secondary settler into the primary holding section 15. The tangential deliveries into the primary holding section 15 are all in directions favorable Yto imparting swirling action to liquid movement therein,

as indicated by arrows in Fig. 3. The valve-controlled branch pipe 33 has a tangential submerged delivery into the upper portion of the secondary holding-mixing tank 16, whereby there is imparted a swirling motion to the liquid in that secondary tank in the direction indicated by the arrows in Fig. 3. A swirling motion in each of the primary and secondary tank sections 15 and 16 just referred'to is important, or at least helpful, but the direction of the swirl in each one of these primary and secondary tanks 15 and 16 is immaterial. The essential thing is that a swirling motion shall be imparted to each of the bodies of liquid within tanks 15 and 16.

The primary and secondary tanks or tank sections 15 and 16 for holding the swirling or rotating liquid bodies are from 4 to l0() feet in diameter and from 6 to 12 feet deep, with a detention capacity of the order of three hours upwards for so-called complete treatment but of not less than one and one-half hours for intermediate treatment. The dimensions are relatively unimportant in themselves, except as they relate to the holding time to be provided for in the plant. Each tank is such that the feed thereto preferably causes a spiralized vortical flow therein having a Vperipheral speed of the order of from .5 to 1.5 feet per second. The peripheral speed of the liqu'id spiralizing Cit ' region outside of the apparatus.

in each tank is such that ocs formed therein do not tend to be disintegrated. The spiralized action of the liquid in each tank leads to furthering occulation since arcuate planes or cylindrical sections of liquid tend to slip past other such sections at effective occulating speeds. This relative motion between adjacent arcuate films of liquid contributes to the coagmentation of particles of turbidity into flocs and such continued action tends to roil up the flocs to compact them into settleability.

From a lower portion of the secondary tank 16 there extends a valve-controlled secondary oxidized liquid transfer line 53 leading from a lower interior portionof the secondary holding-mixing tank 16 to the secondary settler Y 34 hereinafter referred to. This secondary oxidized liquid transfer line 53 has a positionable control valve 54 therein.

Aerator-colloder 24 thereby to or in operative relationship with respect to the discrete bed 25 and constructed for eecting a relatively uniform distributed delivery of recirculated liquid'passed thereinto and therefrom prior lto treatment or Vrepetitive treatment of the successive quantities of liquid as delivered to and upon the bed of discrete material 25. Since the bed of discrete material is relatively thin and the openings or passageways between the several bodies of discrete material are relatively large, there is a quick passage or transit of the liquid delivered from the distributing means downwardly within, through and from the bed of discrete material; l

It is here to be noted that the depth of this material which I have found as being satisfactory and effective for the purpose intended and which has been used by me is one foot and my recommendation would be that this bed should have a depth of not over two feet.

This aerator-colloider is intended to eifect a major aerating action on the liquid supplied thereto each time it makes a transit through the bed. It also serves to effect a colloiding of particles in the liquid passing through the bed. The colloided liquid'or bed discharge is passed from the colloiderto wit: from the sump 28 thereof-through the transfer line 29 having valve-controlled branch delivery sections 31 and 33 whereby a quantity of the colloided liquid or bed discharge is delivered into the primary tank 15 by the .branch section 31 and a quantity is delivered into the secondary tank 15 by the branch section v33.

Secondray oxidized liquid line 53 and subsequent settler 34 There is a progressive feed of liquid into these tanks and a corresponding discharge of liquid from the secondary holding-'mixing tank 16-to wit: through a secondary oxidized liquid transfer line 53, if desired, having valve 54, into the liquid receiving and holding section of a secondary orsubsequent settler 34, from which settler clarified liquid can pass as overflow over Weir edge 35 into an effluent launder 36 and thence as stabilized clarified liquid vby means of the efliuent pipe 37 leading to a This discharge of stabilized purified efuent from the line 37 substantially corresponds in quantity to that of the inflowing liquid supplied to the primary holding-mixing tank 15 by the line 14 which serves as a feed line leading into the primary holding-mixing tank 15. This secondary oxidized liquid line 53 is equipped with means for releasing from the apparatus a quantity of liquid substantially equal to that of the quantity of feed liquid directed into the primary holding-mixing tank for treatment. may be provided by an outlet control means such as an Such liquid release overow weir 35, whence the flow passes through the efduent line 37. Valve 54 is not actually necessary to the operation of the system, since the ow from the holding-mixing tank to the secondary settler is by gravity and the liquid-level in the holding-mixing tanks is automatically controlled by the elevation of the overow weir 35 in settler 34. The valve can be used in shutting down the system for repairs.

Subsequent settler 34 and return sludge line 39 Eiuent from the settler 34 by means of Weir 35 determines the liquid-level in the holding-mixing station 20. Underow from that settler 34 is passed by the return sludge line 38-past the valve 39 thereof-and into the section 40 of the return sludge line to a branching pump line 42 controlled by valve 43 leading to pump 44 having a pump outiiow section 45 leading into the gravity ow feed line 14 leading into the primary holding-mixing tank 15. This is a condition existing when the valve 41 is closed. If the valve 43 of line 42 is closed and the valve 41 of the return sludge section 40 is open, then there can be a transfer of sediment or outflow from the second settler to a locality outside of the apparatus for disposal thereof. in connection with the foregoing it will be observed that the detaining and mixing station 20 is connected in cycle path arrangement by the gravity ow secondary oxidized liquid line 53 leading from a low interior portion of the secondary holding-mixing tank 16 to and into the secondary or subsequent settler 34, thence along return sludge line 38 and section 40 into pipe section 42 leading into pump 44 and from the latter by the pipe or line 45 to the feed delivery section of gravity ow line 14 and thus tangentially into the upper interior circular section of the primary holding-mixing tank 1S.

A contemplated example of an embodiment of this invention is as follows:

Primary and final clariiiers Holding-mixing tanks Aerator-colloider 30' dia. x 8' deep 3o' am. x 12' deep 30 dia. x l deep (700 sq. ft.; 30% voids) Recirculaton pumpseach 2800 g. p. m. Type of Waste Domestic sewage Detention period:

Clariers-each 2.87 hours Mixing tankstotal 8.60 hours Recirculation ratio 115 Transit time through colloider 30 seconds Recirculation (2800 g. p. m.) .2 cfs. Estimated B. O. D. reduction 90% From that which has preceded it is believed the manner of performing or realizing the advantageous features of construction and of the operative steps of the new process constitute the basis of certain phases of the invention which will be readily understood and appreciated.

The bed of the aerator-colloider functions as a biologic bed and in connection therewith it will be noted that this bed has to be initially inoculated with aerobic biologic organisms of a character capable of establishing and maintaining certain biological functions and development in the liquid flowing through the bed, which is not only aerated while iiowing therethrough but is also further biologically treated while in transit through, from, within and leading into the detaining and mixing station 20. Such a station can be used to advantage especially when embodying the teachings of my co-pending application Ser. No. 705,127, now abandoned, tiled December 9, 1946 of which parent application this application is a continuation-in-part.

I claim:

1. In a process of treating sewage, the steps comprising establishing a colloider bed of discrete solids having a bed depth of from one to two feet, inoculating the bed with aerobic biologic organisms capable of purifying the sewage, supplying clarified sewage to a detention and mixing zone, detaining it there for at least one and a half hours, meanwhile mixing therein such sewage with activated sludge, passing through the bed such mixture drawn from the zone, and returning liquid that has passed through the bed to the zone with the rate of passage being at a velocity such as to ush from the bed zoogleal films substantially as fast as formed as well as to impel any one drop of liquid to transit through the bed in from 40 to l0 seconds.

2. The steps according to claim l, wherein liquid from the mixing and detention zone is passed to the colloider bed at a rate equal at least to substantially 10 times that detained volume.

3. The steps according to claim 1, with the addition of flowing treated liquid from the mixing zone to a body of such liquid held in quiescent sedimentation, and controlling the liquid-level in the mixing zone by the liquidlevel in the quiescent body.

4. The steps according to claim l, wherein the detention and mixing is carried out in sequence by vortically rotating the liquid and sludge in a primary and a secondary cylindrical liquid body of substantially equal size but at different vortical speeds, and conducting aerated eflluent from the secondary body back ahead of those bodies in the treatment system.

5. The steps according to claim 4, with the discharge from the colloider bed passing some to one and some to the other of the two vertically rotating bodies.

6. The continuous biologic process of treating polluted liquids, which comprises supplying feed for treatment in a system including a shallow biologic filter bed of discrete material and a detention zone, controllably passing effluent from the detention zone through the filter bed at a rate maintained to lie in a range of from 200 to 800 million gallons per acre per day and the time of passage of the liquid through the bed to lie in a range of from l0 to 40 seconds, returning discharge from the bed to the detention zone having a detention capacity of from 3 to 24 hours inow of feed supplied to the system, and releasing biologically stabilized liquid from the system.

7. Those steps in sewage treatment that comprise establishing and maintaining a bed of discrete solids having a bed-depth not substantially in excess of two feet, establishing and maintaining inoculation of the bed with aerobic biologic organisms capable of purifying sewage, applying sewage liquid to the bed, and passing it therethrough in volume to lie in a range of from substantially 200 to substantially 800 million gallons per acre per day to impel any one drop of liquid to transit through the bed in from 40 to l0 seconds with the faster being the better.

References Cited in the le of this patent UNITED STATES PATENTS 2,021,679 Bevan Nov. 19, 1935 2,077,498 Streander Apr. 20, 1937 2,120,634 Stevenson .lune 14, 1938 2,142,196 Langdon Ian. 3, 1939 2,348,126 Green May 2, 1944 2,355,760 Trebler Aug. 15, 1944 2,528,887 Kickhoefel et al. Nov. 7, 1950 2,562.510 Schlenz July 31, 1951 

6. THE CONTINUOUS BIOLOGIC PROCESS OF TREATING POLLUTED LIQUIDS, WHICH COMPRISES SUPPLYING FEED FOR TREATMENT IN A SYSTEM INCLUDING A SHALLOW BIOLOGIC FILTER BED OF DISCRETE MATERIAL AND DETENTION ZONE, CONTROLLABLY PASSING EFFLUENT FROM THE DETENTION ZONE THROUGH THE FILTER BED AT A RATE MAINTAINED TO LIE IN A RANGE OF FROM 200 TO 800 MILLION GALLONS PER ACRE PER DAY AND THE TIME OF PASSAGE OF THE LIQUID THROUGH THE BED TO LIE IN A RANGE OF FROM 10 TO 40 SECONDS, RETURING DISCHARGE FROM THE BED TO THE DETENTION ZONE HAVING A DETENTION CAPACITY OF FROM 3 TO 24 HOURS INFLOW OF FEED SUPPLIED TO THE SYSTEM, AND RELEASING BIOLOGICALLY STABILIZED LIQUID FROM THE SYSTEM. 